A semiconductor memory array includes a plurality of unit memory cells that are electrically connected to one another. In dynamic random access memory (DRAM), for example, a unit memory cell may include one switch and one capacitor. A DRAM has high integration density and high operation speed. However, when power is not supplied to the DRAM, data stored in the DRAM is erased. An example of non-volatile memory is flash memory, in which stored data is not erased when power is not supplied. Although flash memory has non-volatile characteristics, flash memory has low integration density and low operation speed as compared to DRAM.
Many modern day electronic devices contain electronic memory configured to store data. Electronic memory may be volatile memory or non-volatile memory. Volatile memory stores data while it is powered, while non-volatile memory is able to store data when power is removed. Resistive random access memory (RRAM) is one promising candidate for next generation non-volatile memory technology due to its simple structure and CMOS logic compatible process technology that is involved. An RRAM cell includes a dielectric data storage layer having a variable resistance, which is placed between two electrodes disposed within back-end-of-the-line (BEOL) metallization layers.
Resistive random access memory (RRAM) is one of the non-volatile memory devices. An RRAM is a resistive type memory based on a characteristic that a resistance of a transition metal oxide varies according to a voltage applied thereto, and the resistance is used to store a bit of data in an RRAM cell instead of an electronic charge used in the DRAM. An RRAM consists of a capacitor like structure in which the insulating materials show a resistive switching behavior.